The present invention generally relates to image data processing apparatuses, and more particularly to an image data processing apparatus suited for carrying out an image data compressing process of an electronic still camera which uses solid state image sensors.
Electronic still cameras which use solid state image sensors such as charge coupled devices (CCDs) have been developed to replace the conventional still camera which uses the silver-salt photography technique. The electronic still camera converts light from an object into an electrical signal and records this electrical signal on a recording medium after subjecting the electrical signal to an appropriate signal processing.
FIG. 1 shows an example of a conventional electronic still camera. Light L from an object is imaged on an image sensor 52 via a lens 50 and a shutter 51. A driving circuit 53 subjects the imaged light to a photoelectric conversion and an analog image signal is output from the image sensor 52. The analog image signal is formed into a video signal such as a television signal in a signal processing circuit 54. The output video signal of the signal processing circuit 54 is converted into a digital video signal in an analog-digital (A/D) converter 55 and is temporarily stored in a buffer memory 56 which can store the video signal amounting to one picture. The video signal stored in the buffer memory 56 is subjected to a data compression in a coding circuit 57 and is stored in a memory pack 58.
When picking up an image on the electronic still camera, various adjustments must be made including focal adjustment, exposure adjustment and white balance adjustment. Conventionally, such adjustments require the use of sensors provided exclusively for the adjustments and there is a problem in that it is difficult to realize an inexpensive electronic still camera. In addition, the electronic still camera must have compatibility with other electronic still cameras on the market, and there is a need to standardize the coding system which is employed in the coding circuit 57.